In the photo I have made a fixed charge +Q . In the book I read the electric potential at infinity is 0 and to bring charge from infinity to point we have to do work against the repulsive force . And that work is the electric potential at point A. We say that we do work against the repulsive but do the mass of the +q charge containing body influence the amount of work done or we consider that mass to be negligible. Please clear my doubt. If there is a misconception then please clear it as I don't know much about physics.
We just consider the work made by Coulomb's force and not the total work made on the charge. If it wasn't this way the definition of potential would depend on the forces or paths chosen to calculate the work.
P.S. I'm sorry if I made grammatical mistakes, I'm not used to writing in English